1. Field of the Invention
This invention relates to a carbon fiber reinforced structural beam
2. Description of Related Art
Carbon fiber reinforced polymer (CFRP) composite, also know simply as “composite”, is not only very strong but light weight as well. Typically, layers of woven or non-woven fabric of carbon fibers are placed in a matrix of a polymer such as epoxy, polyester, polyamide, or polyvinyl. In this regard, composites are similar to the widely employed fiberglass reinforced polymer. Composites are becoming the material of choice for aircraft, high performance automotive applications, machine parts, and sporting gear. As the relative cost of composites drops with the development of more efficient manufacturing techniques, we will, no doubt, see a greater use of composites in future.
In recent years, civil engineers have increasingly used CFRP as a means to reinforce concrete, wood, and metal structural elements. See for example, Buell, et al., Journal of Structural Engineering, vol. 131, No. 1, pp 173-187 (2005), U.S. Pat. No. 7,100,336, US patent, and Japanese patent JP 2001-020461A. Currently, composite structural beams are available in the various shapes that mimic metal beams.
While the strength and light weight of composite beams are attractive, connecting such composite beams both with other composite elements and with metal elements is problematic. They can not be welded like metal beams and bolting or riveting can lead to stress fractures, which subsequently lead to failure of the beam. Special fittings can be used to join composite elements, but require special techniques, with which construction workers are often not familiar, thus slowing assembly. Further, exposed composite beams are often subject to cuts and abrasion, particularly during construction, leading to future failure of the beam. Composite beams degrade when exposed to ultra-violet light, so they must be shielded from direct sun light. For example, U.S. Pat. No. 4,654,242 teaches a multi-layer composite beam but does not teach a protective cover for such a beam. Because composite and metal structural elements have quite different coefficients of thermal expansion, such differences must be accommodated when ever metal and composite materials are coupled.